In an overhead travelling carriage system, an article is conveyed by running an overhead travelling carriage along a running rail installed close to a ceiling in a clean room or the like. An overhead buffer can be effectively installed close to a load port (a ground workstation provided in a processing device or the like) in order to increase the efficiency of the overhead travelling carriage system. The Japanese Patent No. 3067656 proposes provision of an overhead buffer between load ports and below the running rail. However, if load ports are consecutively arranged, there is no space enough to provide the overhead buffer between the load ports.